The following methods have been known conventionally as the marking method on resin molding by using energy ray such as laser beam. As disclosed in Japanese Patent Publication No. 61-11771 and Japanese Patent Publication No. 62-59663, a resin is mixed with a filler which is deformed by the action of the laser beam or energy ray, and the mixture is injection-molded to obtain a resin molding. The resin molding is exposed to energy rays such as a laser beam to be partly discolored, so that a desired character or pattern is formed. As disclosed in Japanese Laid-open Patent No. 60-4094 and Japanese Laid-open Patent No. 1-267092, a plurality of coat films are formed on the surface of a resin molding by applying paints of different colors and only the surface layer or a plurality of coat films are partially removed by a laser beam, so that the desired color is left over.
Exemplary conventional methods are described below while referring to FIG. 12 and FIG. 13. FIG. 12 is a front view for explaining a method of discoloring the filler in the resin molding, and FIG. 13 is a sectional front view for explaining a method of removing the coat film of the paint on the resin molding. In FIG. 12, the surface layer containing a paint powder 4 which is discolored by the action of a laser beam is formed on the surface of a resin molding 3. A laser beam 1 controlled by a deflection device 2 is emitted to the surface layer, and the portion exposed to the laser beam is changed in color, and a mark 5 is formed. As the laser beam 1 is emitted by deflection control according to the desired character or pattern, the mark 5 is formed on the surface layer of the resin molding 3.
In FIG. 13, three color paints are applied sequentially on the surface of a resin molding 6, and three layers of coat films 7, 8, 9 are formed. A laser beam 1 controlled by a deflection device 2 is controlled in reflection according to the emitting position corresponding to a desired character or pattern, and is also controlled in the amount of energy, and is emitted to the surface coat film 7 side of the resin molding 6. Depending on the amount of energy, the coat film 7, coat film 8 or coat film 9 having a different color is cut off, and characters and patterns having different colors are formed as required.
However, in the conventional marking method by making use of discoloration of the filler of the resin molding by laser beam, characters or patterns of different colors cannot be formed on one resin molding. On the other hand, in the conventional marking method by removing the coat film partly by irradiation with laser beam by preliminarily formed coat films on the surface of the resin molding, by forming coat film layers in multiple layers by different colors, combination of various color marks is possible, but it requires more steps in coating and drying.
It is hence an object of the invention to present a method of marking desired characters or patterns, and making the molding with different colors, not limited in mark color, at low cost.